5987233b99
Put them in a separate file for separation of concerns (making them testable) and add some tests.
59 строки
1,7 КиБ
Go
59 строки
1,7 КиБ
Go
package cgo
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// This file implements a parser of a subset of the C language, just enough to
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// parse common #define statements to Go constant expressions.
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import (
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"go/ast"
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"go/token"
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"strings"
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)
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// parseConst parses the given string as a C constant.
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func parseConst(pos token.Pos, value string) *ast.BasicLit {
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for len(value) != 0 && value[0] == '(' && value[len(value)-1] == ')' {
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value = strings.TrimSpace(value[1 : len(value)-1])
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}
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if len(value) == 0 {
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// Pretend it doesn't exist at all.
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return nil
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}
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// For information about integer literals:
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// https://en.cppreference.com/w/cpp/language/integer_literal
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if value[0] == '"' {
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// string constant
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return &ast.BasicLit{ValuePos: pos, Kind: token.STRING, Value: value}
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}
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if value[0] == '\'' {
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// char constant
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return &ast.BasicLit{ValuePos: pos, Kind: token.CHAR, Value: value}
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}
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// assume it's a number (int or float)
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value = strings.Replace(value, "'", "", -1) // remove ' chars
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value = strings.TrimRight(value, "lu") // remove llu suffixes etc.
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// find the first non-number
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nonnum := byte(0)
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for i := 0; i < len(value); i++ {
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if value[i] < '0' || value[i] > '9' {
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nonnum = value[i]
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break
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}
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}
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// determine number type based on the first non-number
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switch nonnum {
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case 0:
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// no non-number found, must be an integer
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return &ast.BasicLit{ValuePos: pos, Kind: token.INT, Value: value}
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case 'x', 'X':
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// hex integer constant
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// TODO: may also be a floating point number per C++17.
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return &ast.BasicLit{ValuePos: pos, Kind: token.INT, Value: value}
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case '.', 'e':
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// float constant
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value = strings.TrimRight(value, "fFlL")
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return &ast.BasicLit{ValuePos: pos, Kind: token.FLOAT, Value: value}
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default:
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// unknown type, ignore
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}
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return nil
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}
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